1. Field of the Invention
The invention herein relates to lights and infrared and video cameras used for search and surveillance, particularly from aircraft. More specifically it relates to apparatus and methods for synchronizing the operation of such devices.
2. Description of the Prior Art
Use of aircraft, particularly helicopters, for aerial search and surveillance of terrain is commonplace. In search and rescue missions, for instance, the aircraft may be used to hunt for missing or lost persons in rural or wilderness locations, hunt for injured hikers or the like. While in some cases such missions are conducted only in daylight hours, in many cases they are also conducted through twilight and night hours, particularly when the person being sought is especially at risk because of age, infirmity or threatening weather conditions. Further, while usually the person being sought is actively seeking to be found and tends to make himself or herself as visible as possible to the aircraft crew, there are certainly many instances where the aircraft crew must actively hunt for the individual. This is true, for instance, where the missing person is a small child, a mentally impaired person or where the person has been injured and is either immobilized or unconscious.
As important as the foregoing situations are with respect to life and safety, they are conducted in an atmosphere of cooperation or at least neutrality between the aircraft crew and the person being sought. In law enforcement aerial search and surveillance, however, the atmosphere is one of adversarial circumstances accompanied by deliberate efforts on the part of the person being sought to avoid being found by the aircraft crew. Typical of such situations are a criminal fleeing from the scene of a crime or an illegal alien attempting to enter the country surreptitiously.
Various governmental agencies maintain one or more aircraft for such search and surveillance purposes, including but not limited to the U.S. Coast Guard, the Border Patrol of the U.S. Immigration and Naturalization Service, the U.S. National Park Service, and numerous federal, state and local law enforcement agencies. In most cases, these aircraft are helicopters of various types, because of the mobility and versatility of helicopters as compared to fixed wing or even vertical takeoff and landing (VTOL) aircraft. Therefore, to exemplify the invention in the description herein, it will be assumed that the aircraft in question is a helicopter, and, as is typical, that the helicopter has a two person crew, a pilot and an observer.
Search and surveillance helicopters are commonly equipped with two principal types of search and surveillance devices. The first is a high intensity lamp such as a searchlight, mounted in motorized gimbals on the outside of the helicopter and controlled by the observer sitting in the helicopter The observer looks through the helicopter windows and watches the projection of the searchlight on the ground, to follow the movements of a person or a vehicle on which the searchlight is focused. The observer also simultaneously watches through the helicopter windows for surrounding activity, particularly when monitoring the movements and presence of vehicles other than the target vehicle during a pursuit.
The other major type of device carried by search and surveillance helicopters is a video camera, an infrared camera, or a combination of the two. Such cameras are also mounted in motorized gimbals on the outside of the helicopter, but are mounted independently of the searchlight mounting. Both devices send their images to a video monitor mounted inside the helicopter and watched by the observer. The infrared camera is used for detecting persons in the dark or when they are not readily visible because of camouflage or hiding in brush, areas of debris, litter, construction, etc. As is well known, infrared cameras detect targets by thermal radiation differences between the target object and the background, the most common of which is to detect a person's body heat against the cooler background of his or her surroundings. Video cameras are used primarily to obtain a record of the search and surveillance, such as in vehicle pursuits where the target vehicle's speed and movements are recorded for subsequent law enforcement or prosecution purposes.
In most instances, it is important for the observer to use both the searchlight and camera simultaneously, to take advantage of the synergistic effect of the different capabilities of the various types of equipment. However, since the searchlight beam, the terrain and other surroundings must be monitored by watching through the helicopter windows, while the infrared and/or video camera's image must be watched on the video monitor within the helicopter, it is extremely difficult for the observer to handle both things at the same time, particularly since he or she must also simultaneously operate two different hand controls to aim the searchlight and camera in the desired directions.
Merely physically mounting the searchlight and the camera together physically, in a manner such as that depicted in U.S. Pat. No. 4,027,159, is not a practical solution, since in many cases it is necessary or desirable to have the camera aimed in a different direction from the searchlight. For instance, when pursuing a fugitive through brush, law enforcement officers often want to detect the fugitive with the infrared camera but avoid having the fugitive aware that his presence has been detected. To do this the searchlight is aimed in a different direction from the camera so that the fugitive, seeing the light beam some distance away, thinks detection has been successfully avoided.
There have in the past been several types of systems which have been disclosed for operating two or more externally mounted pieces of equipment on a helicopter to be operated simultaneously or in conjunction with each other. Typical examples include a camera system for aiming weapons from a helicopter gunship which is disclosed in U.S. Pat. No. 3,641,261. In this system, the cameras are fixed in position, and the pilot and copilot must cooperate in using mirrors to aim movable gun turrets in unison. The system is complex and cannot be operated by a single person. Other systems include those shown in U.S. Pat. Nos. 4,084,083; 4,093,904 and 4,245,298. All of these systems, however, are also quite complex, in that they rely on the inclusion of an additional device to receive and coordinate signals from each of separate search and surveillance devices, and then independently operate each device (e.g., weapons turrets or camera). Thus, each search and surveillance device is separately operated by the coordinating unit, rather than having one of the search and surveillance devices (the "master") directly control the synchronization of the other device (the "slave"). In addition, such systems are expensive because Of the additional equipment needed, and failure of the coordinating unit can render the individual devices and the entire system inoperative.